NASA doesn’t care if you have a hot body or not. Tall, short, lumpy, lithe—as long as you’re fit and fall within a reasonable height and weight range, you clear at least one simple hurdle to becoming an astronaut. But NASA isn’t Hollywood. And so, in the new—and extraordinary—movie Gravity, when Sandra Bullock comes inside after a spacewalk, she shucks her pressure suit and floats about in a crop-top and boxer briefs, perfectly toned, perfectly lovely, zero-g eye candy.

In truth, what an astronaut returning from what NASA calls extavehicular activity (EVA) would have on under her pressure suit would be what’s known as a Liquid Cooling and Ventilation Garment, a full-body, crazily complex bit of space finery that has about 300 ft. (91 m) of fashionable plastic tubing running through it. She’d also be wearing an adult diaper and would be wringing with sweat. Doesn’t matter if you’re Bullock, Penelope Cruz or Nicole Kidman, you would not be looking your best.

It’s really beside the point to mention any scientific inaccuracies in Gravity since the movie is so gripping, so jaw-dropping, so visually, gobsmackingly good that it seems churlish to pay attention to much else. What’s more, Gravity, which does get much more right than it gets wrong, is not Apollo 13 or The Right Stuff—movies that had to hew close to history because they were based on real events. (Disclosure: I wrote the book on which Apollo 13 was based and served as a consultant on the movie.) Gravity is a space disaster and survival movie that never happened in real life—though in smaller and surely less cinematic ways it could.

All the same, science is science and facts are facts and when a movie purports to traffic in both, it’s only fair to point out the blunders—none of which were howlers in this case, but at least some of which could (and should) have been avoided. Spoilers, by the way, lurk here like satellite debris, so proceed with caution if you haven’t yet seen the movie.

The triggering incident in Gravity—equivalent to the exploding oxygen tank in Apollo 13—occurs when Russia launches a missile to destroy one of its own satellites, accidentally creating a chain reaction that demolishes most of the communications satellites orbiting the planet. An American space shuttle is in orbit on a Hubble Telescope repair mission at the time, and not only does the satellite disaster plunge the crew into radio blackout, it also puts them directly in the path of a high-speed swarm of space junk that whips around the planet every 90 minutes. The shuttle gets clobbered, most of the astronauts die, something less than hilarity ensues. So, where to begin?

First of all, the Hubble orbits at an inclination of 28.5º, which maximizes the time it spends passing over the American mainland on its various trips around the planet. The shuttle, in most cases, stays at that angle too. Russian satellites, however, orbit at higher inclinations, for the same reason—to keep them as close as possible to the Motherland. Junk from a Russian pigeon-shoot might cross the shuttle’s orbit on some of its passes, but it would not happen right away—and certainly not every hour and a half. After the shuttle is destroyed, the surviving astronauts seek refuge on the International Space Station, which is conveniently located nearby. But the ISS orbits at 51.6º—a concession to the Russians when we built the station, since their Soyuz spacecraft regularly ferry crews up and down. Shuttles fly at that high inclination when they’re visiting the ISS, but they wouldn’t be anywhere remotely in the neighborhood if they were servicing Hubble.

What’s more, a satellite-demolishing chain reaction would never happen in the first place. In 2008, the U.S. shot down one of its own dead satellites—ostensibly to prevent it from spinning out of control, but probably as a military riposte to China, which had pulled off a similar bit of cosmic marksmanship the year before. The technology needed to clean up your own dead satellites is pretty much identical to what it would take to shoot down another country’s very much alive ones, and China was no doubt signaling that it had the wherewithal. So do we, we signaled back, so do we. In neither case was there a risk of anything like what occurred in Gravity, and while you could probably write a computer model that would show how such a thing could happen, it’s wildly improbable.

Then there was all the spacewalking. When the movie opens, we see Bullock and another crewmember hard at work on the Hubble and the shuttle, while George Clooney, wearing a Manned Maneuvering Unit (MMU, essentially a space jet pack) zips around them, having a grand time as he listens to country music and wisecracks. It’s the only bit of the movie that looks slightly silly—and it also grossly overstates the speed and maneuverability of the MMU. What’s more, NASA would never countenance such cosmic silliness because the MMU’s fuel was limited and could easily run out—something that in fact happens in the movie. When disaster strikes and Clooney is adrift, it’s fair to wonder if his character wishes he’d cooled it a bit on the earlier horseplay. Bullock, who is not wearing an MMU, finds herself in similar free-floating peril. While spacewalking astronauts wear tethers, they are also equipped with a small backpack called SAFER (Simplified Aid for EVA Rescue) which would allow them to maneuver back to the safety of the ship if the tether should break. Bullock’s does, but she has no SAFER. Later, when she improvises, using a space station fire extinguisher as a sort of handheld jetpack—well, suffice to say that actually maneuvering with such a thing would be far less successful than it is on screen.

There are other implausibilities too. Bullock winds up piloting two other countries’ spacecraft: a Russian Soyuz and a Chinese Shenzhou, which she picks up when she makes her way to China’s space station—which exists, sort of, but only as a single pod, not as the sprawling complex it appears in the movie, and in either case it orbits at 42.78º, nowhere near the Hubble and the shuttle. She handles both ships with surprising deftness considering she was only lightly trained on the Soyuz and not at all on the Shenzhou. And throughout the movie, she and Clooney spend a fair bit of time getting whacked around in space, grabbing onto this or that rail or tether on the shuttle or ISS only at the last second to avoid pinwheeling off into the void. In truth, pressurized space gloves are murderously hard to manipulate, providing only limited grip at best and leaving astronauts’ hands cold and very painful after a day of work. Making the kinds of one-handed Cirque du Soleil catches Clooney and Bullock accomplish would be impossible.

So, that’s a lot that Gravity gets wrong. But you know what? So what? The shuttle, space station and spacesuits are painstakingly recreated; the physics of moving about in space—thrusts requiring counterthrusts, spins requiring counterspins, the hideous reality that if you do go spiraling off into the void your rotation never, never stops—are all simulated beautifully, scarily and accurately. Gravity will wind you up and wring you out as only the best thrillers do. Absolute technical accuracy matters—except when it doesn’t. Gravity gets a well-earned waiver.